Jolly-looking balls of floating necroplasm that can be found in all of the various DOOM games. They belch balled lightning from a distance and take tasty chunks out of space marines with their gaping jaws at close range.

DOOM 64 Cacodemons, while they behave identically to the standard version, look somewhat different, due to the last, barely-surviving demon, the Hell-Mother, altering the appearance of its offspring when it began single-handedly repopulating Hell (I guess a little amnesia is in order when you take a BFG blast to the head...)